Various liquids are conventionally stored in bulk quantities in storage tanks in locations throughout the world. For instance, storage tanks are used extensively for the storage of petroleum products such as gasoline wherein large steel and/or fiberglass vessels are buried in underground locations such as at retail gasoline stations. In most instances, such stations are in populated areas where there is a significant danger associated with leaks from the storage tanks.
Initially, such tanks are well suited for their intended purpose since the highly volatile contents are safely contained. Moreover, they are in a location where they are not readily subject to ignition by any external means which might otherwise cause a fire or explosion. However, after a number of years, such storage tanks often deteriorate by reason of exposure to harsh environmental conditions, particularly for steel tanks.
When such deterioration occurs, the storage tank contents leak from the tank at an unknown underground location. This causes not only loss of the valuable contents, but also possible environmental contamination and health hazards as well as the existence of a potential hazardous condition which typically developed over time inasmuch as any leaks are normally very slow initially. Equally important, ground water then leaks into such underground storage tanks causing a contamination of the liquid stored therein.
To overcome this problem, underground storage tanks have more recently been formed of various plastic materials that are less susceptible to deterioration. These tanks, when typically used for storing gasoline or other liquids, commonly have inner and outer walls spaced apart by a relatively great distance with the walls typically being reinforced by ribs therebetween, but such tanks have been undesirably large, heavy and require much more material for their construction. Moreover, ground water and/or gasoline may leak into the space between the inner and outer walls in the event of a defect in which case the leaking liquid will drain to the lower regions thereof.
With this dual-walled plastic construction, it is generally recognized that significant advances have been made over steel storage tanks in terms of long term avoidance of corrosion. It is nevertheless known that despite the advances to date, there is still a recurring problem of failure of the inner and/or outer walls of such storage tanks which is the reason it has been proposed to place sensors in the lower regions of such tanks capable of providing warnings of any leakage. When leaks do occur in the field, the problem is necessarily serious since gasoline and/or ground water will be contained within the space between the two walls of the tank.
Understandably, it is desirable to have a warning of any leakage in such storage tanks which accounts for the interest in sensors. Furthermore, sensors are now such that the custodian of tank can actually tell whether the liquid leaking into the space between the walls is, for instance, ground water or gasoline. In such manner, it is possible to know not only that there is a leak but also whether the leak is occurring in the inner or outer wall of the storage tank.
Unfortunately, such sensors do nothing toward the major objective of entirely eliminating the possibility of such leaks. Even more significantly, there is no containment of the total storage tank system, i.e., not only the storage tank itself but also access openings and pipeline systems associated therewith. While efforts to this end have been made in U.S. Pat. No. 4,685,327, there is still no entirely satisfactory leak detection system.
In this connection, it is generally known that a significant percentage of leaks occur in access openings and pipeline systems. Thus, whether a leak should occur in or through a manhead, or in any of the pipes normally associated with a storage tank, whether those pipes extend first through a sleeve surrounding a manhead or extend directly into a storage tank, it is important to provide a leak detection system. Moreover, an entirely satisfactory type of liquid confinement leak detection system would find wide-ranging applicability.
The present invention is directed to overcoming one or more of the problems and accomplishing one or more of the objectives as aforementioned.